The development of wind energy plants being constructed inland is making use of increasingly higher hub heights above 100 m, in order to utilize the higher and more constant wind speeds and thus improve the efficiency of these wind energy plants. Higher tubular towers with larger and more powerful rotors and generators, however, require at the same time an increased wall thickness and diameter of the tower segments, in order to meet the resulting larger structural mechanics requirements such as rigidity, buckling safety, and endurance strength. But the increasing of the diameter of the tower segments means that the transport of the prefabricated tubular tower segments is no longer possible on many roads due to restrictions, such as bridge clearance of 4.4 m, with the conventional transversely oriented mode of construction.
One possible approach to a solution, proposed for example in DE 603 17 372 T2 and also in WO 2009/048955 A1, is the so-called lengthwise oriented mode of construction, especially in the lower tower region, where the diameters of the finished tubular tower segments are ultimately more than 4.4 m. In this case, tubular tower sections are assembled only at the construction site, i.e., the location of the wind energy plant, from several arc-shaped shell segments and the tubular (annular) tower segments so produced are connected to the full tower. To avoid welding at great height, the shell segments are provided with perforated horizontal and vertical flanges in the tower construction known from DE 603 17 372 T2, enabling a connection of the shell segments by screwing. However, this approach to a solution has some drawbacks. Thus, e.g., in the case of large shell segments, deformations are to be expected from the weight of the shell segments themselves, which can lead to problems of handling and fitting together. On the other hand, when broken up into many small shell segments, the number of screw connections to be made is relatively large, which increases the assembly cost as well as the maintenance cost for tightening up the screws.
Besides wind energy plants with tubular tower and wind energy plants with lattice tower (framework tower), there are also wind energy plants with hybrid construction towers, having a lower lattice tower (framework tower) and an upper tubular tower joined to it.
A tower of a wind energy plant is known from DE 10 2006 056 274 A1, having a lattice tower in the lower part with at least three corner posts and a tubular tower in the upper part with a round cross section, while in the transition zone the upper connection region of the lower part is joined by means of a transition body to the lower connection region of the upper part. The transition body is fashioned as a kind of truncated conical shell, while the respective corner post protrudes into the transition zone and is joined to the outside of the truncated conical shell by two longitudinal weld seams in the transition zone between the upper connection region of the lower part and the lower connection region of the upper part. The corner posts are formed from standardized hollow profiles, preferably steel pipes. Furthermore, the lattice tower has intersecting braces which join the corner posts together.
From DE 103 39 438 A1 there is known a wind energy plant which is likewise constructed from a lower tower section configured as a lattice tower having at least three corner posts and an upper tower section configured as a tubular tower, while a transition piece (transition body) is arranged between the upper and the lower tower section, having a lower region and an upper region, while the lower region can be joined to the lower tower section and the upper region to the upper tower section. The lower region of the transition piece is configured such that its largest horizontal dimension is at least 30% larger than a horizontal dimension of the upper region. The transition piece is configured as a cast iron part or a welded construction.